The objective of this proposed project is to analyze 24 non-H-2 histocompatibility antigens that are being carried individually in congenic lines of mice. The independence in eliciting immune responses by these antigens when combined in a single graft will be tested. The ability of non-H-2 antigens to induce hemagglutinating, cytotoxic, and blocking antibody will be examined to ascertain the importance of humoral antibody in graft rejection. The distribution of these antigens among adult tissues and their time of appearance in development will be determined to distinguish whether these antigens are important in functions specific to cell type or in functions common to all cells.